This invention relates to a radio system utilizing a synthesizer, the frequency thereof being controlled by data read out of an EPROM.
With recent development of communication systems of various types, a radio system has been desired which is capable of switching a number of frequencies.
FIG. 1 is a block diagram showing one example of a prior art radio system. When an operating frequency to be used is set by a channel switch 1, a read signal generator controlled thereby produces a read signal constituted by a plurality of bits which is supplied to an EPROM 4 acting as a memory circuit. The EPROM 4 is previously written with data so that when a read signal is applied, the written data are read out and supplied to a synthesizer 5. The synthesizer 5 generates a signal having a frequency corresponding to the data supplied from EPROM 4 and the signal determines the operating frequency of a transmitter 6 and a receiver 7. There are also provided a connector 8, an antenna 9 and a loudspeaker 10.
With such a prior art system, however, the read signal generator 2 is required to simultaneously generate a plurality of bits constituting a read signal and accordingly, the number of signal lines that interconnect read signal generator 2 and EPROM 4 increases so that when it is desired to control the frequency by using an EPROM 4 formed on an independent substrate, the number of pins of the connector 8 increases, thus increasing its manufacturing cost and decreasing reliability.